In this international, multicenter trial, 630 HIV infected patients who have not received any previous treatment for their HIV-infection will be enrolled. Participants will be randomized equally (1:1) to receive truvada (tenofovir and emtricitabine) with either the standard or reduced dose of EFV. Neither the study doctor nor the participant will know which treatment the participant is receiving. Physical examinations, laboratory analyses and questionnaires will be performed at the 11 study visits at screening, baseline (Week 0), Weeks 4, 12, 24, 36, 48, 60, 72, 84 and 96. The primary aim of this study is to compare between treatment groups the proportion of patients with undetectable HIV viral load (HIV RNA < 200 copies/mL) after 48 weeks. Information on immune function, drug adherence, resistance to antiretrovirals, quality of life, mental state and HIV-related conditions will also be collected. Blood samples will be collected for future testing. Interim analyses will be performed when the first 125 participants in each treatment group reach week 24 and when all participants reach week 24. These interim analyses will provide an early check that the reduced dose of EFV suppresses HIV infection as effectively as the standard dose of EFV. A follow-up analysis will be performed when all participants reach week 96.